For a pneumatic tire for heavy load for use in a construction vehicle, a significantly high load-bearing ability and a traction performance are required as compared with a pneumatic tire for heavy load such as a tire for use in a truck, bus or light-weight truck. For this reason, conventionally, a so-called rib-lug pattern has been generally employed for a tire tread pattern in which a rib-shaped land portion continuously extending in a tire circumferential direction is arranged in a central region from the viewpoint of wear resistance, and plural lug grooves are arranged in respective side regions from the viewpoint of ensuring traction. However, when the width of the rib-shaped land portion arranged in the central region is too great, the fraction for climbing a hill deteriorates, and a side slippage likely occurs at the time of steering because of absence of the groove extending in the circumferential direction in the central region. Also, sufficient traction cannot be obtained because of absence of a transverse groove in the central region.
In view of the fact as described above, Patent Document 1 discloses a tire in which circumferential narrow grooves defining a central land portion are arranged in a central region to suppress a side slippage at the time of steering, and a transverse narrow groove is arranged on a central land portion to sufficiently improve the traction. In general, when the transverse groove is provided on the central land portion, rigidity at the central land portion decreases, and the wear resistance at the central land portion decreases, accordingly. However, because the groove traversing the central land portion is a narrow groove, the central land portion deforms in the tire circumferential direction due to a friction force between the central land portion and a road surface at the time when the tire rotates under load, and the transverse narrow groove closes in a road contacting region thereof, which causes the adjacent central land portions to be substantially connected with each other. This suppresses the decrease in the rigidity of the central land portion, and also suppresses the decrease in the wear resistance in the central region. Further, outside of the road contacting region, the transverse groove that traverses remains opened, whereby the heat radiation performance of the central land portion effectively improves.
Patent Document 1: JP 2004-262295A